Liquid crystal display device having structure of color filter on TFT and using in plane switching mode

ABSTRACT

A liquid crystal display device includes gate lines crossing data lines on a first substrate defining a pixel region; at least one common electrode formed in the pixel region; at least one pixel electrode in the pixel region, the at least one pixel electrode corresponding to the common electrode; a color filter layer formed within the pixel region excluding the gate line and the data line; a black matrix having at least three layers, an inner layer of the at least three layers being an electrode material.

The present application claims the benefit of the Korean Application No.2004-39344 filed in Korea on May 31, 2004, which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal device, and moreparticularly to a liquid crystal display device having a color filter.

2. Description of the Related Art

With the development of various portable electronic devices such asmobile phones, PDAs, notebook computers, or the like, the demand forlight, thin, and small Flat Panel Display (FPD) devices is increasing.Research is active in the area of flat panel display devices, such as anLCD (liquid crystal display), a PDP (Plasma Display Panel), an FED(Field Emission Display), a VFD (Vacuum Fluorescent Display), or thelike. Currently, interest is in liquid crystal display (LCD) devicesamenable to simple mass-production, using a simple driving system, andproviding high picture quality.

The LCD devices have various display modes according to the arrangementsof liquid crystal molecules. However, among the various display modes,Twisted Nematic (TN) mode liquid crystal display device has widely beenused because of its high contrast ratio, rapid response, and low drivingvoltage. The TN mode liquid crystal display device includes an arraysubstrate on which pixel regions are arranged, a color filter substratefacing the array substrate, and liquid crystals formed between the arraysubstrate and the color filter substrate. In addition, polarizing platesare formed at outer surfaces of the array substrate and the color filtersubstrate such that polarized light may reach the liquid crystals. Inaddition, the liquid crystals are twisted in a spiral shape and arrangedbetween the array substrate and the color filter substrate.

In a related art liquid crystal display device, gate lines and datalines are arranged on the array substrate. Thin film transistors (TFTs)are arranged on the array substrate. Color filter layers for displayingcolor images are formed on a color filter substrate facing the arraysubstrate. Pixels are arranged on the TFT array substrate and the colorfilter substrate to form a matrix of pixels that are precisely alignedto each other. If the pixel regions formed on the TFT array substrateand the color filter substrate are imprecisely aligned, a lightgenerated from a backlight may leak. Thus, the alignment of the TFTarray substrate and the color filter substrate in the related art liquidcrystal device is very important.

To address the misalignment problem, and to focus on a specificsubstrate for fabricating a liquid crystal display device, a liquidcrystal display device having a color filter on TFT (COT) has beenprovided. In the COT liquid crystal device, the color filter layer isformed on the TFT array substrate. In the liquid crystal display devicehaving the COT structure, since the color filter layers are formed onthe TFT array substrate, potentially complicated processes for formingthe color filter may be performed when the TFT array substrate isfabricated. The aperture ratio of the display device may be improved byforming the color filter layers on the TFT array substrate. Also, it iseasier to arrange the TFT array substrate and an upper substrate whenthe TFT array substrate includes the color filter layers.

FIG. 1A is a plan view illustrating a pixel region of a related artliquid crystal display device having a COT structure. Referring to FIG.1, a plurality of gate lines 102 a, and a plurality of data lines 107perpendicularly crossing the gate lines 102 a, define pixel regions. Inaddition, a thin film transistor 130 is formed at one side of the pixelregion. The thin film transistor 130 is connected to the gate line 102 aand the data line 107.

A black matrix 110 is formed at an upper portion of the gate line 102 aand the data line 107. The block matrix 110 blocks unnecessary lightfrom being transmitted from under lower portions of the gate lines andthe data lines. In addition, a color filter layer, including a red,green and blue sub-color filter layers (not shown), is formed in thepixel region. The color filter layer provides color display capabilityfor the liquid crystal display device. A pixel electrode 109 is alsoformed in the pixel region. The pixel electrode 109 applies an electricfield to liquid crystals in the pixel region.

Since the color filter layer is formed on the array substrate on which aTFT is formed, a liquid crystal display device having such a structureis referred to as a color filter on array (COA) or a color filter on TFT(COT).

FIG. 1B is a cross-sectional view along line A-A′ of the related artliquid crystal display device having the COT structure of FIG. 1A.Referring to FIG. 1B, the gate line (not shown) and a gate electrode 102diverging from the gate line are formed on a transparent substrate 101,and a gate insulating layer 103 is formed on the gate electrode 102. Anactive layer 104 of the thin film transistor is formed on the gateinsulating layer 103, and source and drain electrodes 106 a and 106 bare connected to the active layer 104. An ohmic layer 105 is interposedbetween the source and drain electrodes 106 a and 106 b. The data line107 is formed on the gate insulating layer 103. The data line 107 isconnected to the source electrode 106 a and concurrently formed with thesource electrode 106 a. A pixel electrode 109 connected to the drainelectrode 106 b is formed at the pixel region to thereby apply anelectric field to a liquid crystal layer 120. The source and drainelectrodes 106 a and 106 b and the data line 107 are insulated by aninterlayer passivation layer 108. The black matrix 110 and a colorfilter layer 111 are separately formed on the passivation layer 108.

A color filer layer, including red, green and blue sub-color filterlayers, is formed in each pixel region. The black matrix 110 is formedat a reverse tilt domain region, such as the gate line, the data lineand a region where the TFT is formed, thereby preventing light leakage.An upper substrate is located facing the TFT array substrate. The uppersubstrate includes a transparent substrate 150 and the common electrode151 formed on the substrate 150. In addition, alignment layers 112 and152 for aligning the liquid crystals 120 may be further formed on theTFT array substrate. A liquid crystal material 120 is filled between theupper substrate 150 and the TFT array substrate 101.

When fabricating a liquid crystal display device having the COTstructure, processes for forming the black matrix 110 and the colorfilter layer 111 are performed after forming the pixel electrode 109 ineach pixel. Since the black matrix 110 and the color filter layer 111are formed of photosensitive organic layers, photo-mask processes shouldbe performed when forming the black matrix 110 and the color filterlayer 111, respectively. The photo-mask processes increase thefabrication time of a liquid crystal display device. Moreover, aphoto-mask is so expensive that fabrication costs of liquid crystaldisplays increase significantly.

The related art, a color filter layer is commonly formed by a pigmentdispersing method in which red, green and blue sub-color filters areformed by respective photo-mask processes. The color filter layer isformed by using the pigment dispersing method. The black matrix isseparately formed. Accordingly, a total of four photo-mask processes arerequired. There is a strong felt need in the art to reduce the number ofmasks.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device having structure of color filter on TFT and usingin-plane switching mode that substantially obviates one or more of theproblems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method forfabricating a liquid crystal display device having a structure of colorfilter on TFT using a reduced number of fabrication processes.

Another object of the present invention is to provide a liquid crystaldisplay device having a wide viewing angle.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other features, aspects and advantages of the presentinvention will be realized and attained by the structure particularlypointed out in the written description and claims hereof as well as theappended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, aliquid crystal display device includes gate lines crossing data lines ona first substrate defining a pixel region; at least one common electrodeformed in the pixel region; at least one pixel electrode in the pixelregion, the at least one pixel electrode corresponding to the commonelectrode; a color filter layer formed within the pixel region excludingthe gate line and the data line; a black matrix having at least threelayers, an inner layer of the at least three layers being an electrodematerial.

In another aspect, a method of fabricating a liquid crystal displaydevice includes forming gate lines and a gate pad electrode on a firstsubstrate; forming data lines and a data pad electrode on the firstsubstrate; forming an interlayer on the data lines and the data padelectrode; forming a color filter layer on the interlayer; forming apassivation layer on the color filter layer; forming contact holesexposing the gate pad electrode and the data pad electrode; and formingat least three layers on the color filter layer to form a black matrixand a pixel electrode, one of the at least three layers including anelectrode material.

In another aspect, a liquid crystal display device includes gate linescrossing data lines on a first substrate defining a pixel region; atleast one common electrode formed in the pixel region; at least onepixel electrode in the pixel region, the at least one pixel electrodehaving at least three layers, and the at least one pixel electrodecorresponding to the common electrode; a color filter layer formedwithin the pixel region excluding the gate line and the data line; ablack matrix having a same at least three layers as the at least onepixel electrode, an inner layer of the at least three layers being anelectrode material.

It is to be understood that both foregoing general description and thefollowing detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1A is a plan view illustrating a pixel region of a related artliquid crystal display device having a COT structure.

FIG. 1B is a cross-sectional view along line A-A′ of the related artliquid crystal display device having a COT structure of FIG. 1A.

FIG. 2 is a plan view of exemplary pixel regions in an array substrateof a liquid crystal display device having a color filter on thin filmtransistor structure in accordance with an embodiment of the presentinvention.

FIG. 3A is a cross-sectional view of an exemplary pixel region alongline I-I′ in the array substrate of the liquid crystal display device ofFIG. 2.

FIG. 3B is a cross-sectional view of an exemplary gate pad and anexemplary data pad along lines II-II′ and III-III′, respectively, in thearray substrate of the liquid crystal display device of FIG. 2.

FIG. 4A is a cross-sectional view of an exemplary pad unit outside apixel region of a liquid crystal display panel in accordance with anembodiment of the present invention.

FIG. 4B is a plan view of exemplary pad units outside a liquid crystaldisplay panel in accordance with an embodiment of the present invention.

FIG. 5A is a cross-sectional view of the formation of exemplary gateelectrodes and common electrodes in a process of fabricating an arraysubstrate of a liquid crystal device in accordance with an embodiment ofthe present invention.

FIG. 5B is a cross-sectional view of the formation of exemplary thinfilm transistors and data electrodes in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention.

FIG. 5C is a cross-sectional view of the formation of exemplary layersof an interlayer and a color filter in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention.

FIG. 5D is a cross-sectional view of the lamination of exemplary layersof metal, ITO layer and CrOx in the process of fabricating an arraysubstrate of a liquid crystal device in accordance with an embodiment ofthe present invention.

FIG. 5E is a cross-sectional view of the formation of exemplary patternsof black matrix parts and electrodes in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention.

FIG. 5F is a cross-sectional view of the completion of exemplary gatepads and data pads in the process of fabricating an array substrate of aliquid crystal device in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 2 is a plan view of exemplary pixel regions in an array substrateof a liquid crystal display device having a color filter on thin filmtransistor (COT) structure in accordance with an embodiment of thepresent invention. Referring to FIG. 2, a liquid crystal display deviceincludes an array substrate and an upper substrate facing the arraysubstrate. Thin film transistors are arranged in a matrix within thearray substrate. Color filter layers also are formed on the arraysubstrate. A plurality of gate lines 202 a and a plurality of data lines205 crossing the gate lines 202 a define pixel regions on a transparentsubstrate, such as glass. Specifically, an M-number of gate lines 202 aand an N-number of data lines 205 define an (M×N)-number of pixelregions.

A common line 204 a is provided in the pixel region. The common line 204a is parallel to the gate line 202 a. At least one common electrode 204extends from the common line 204 a in the pixel region. The at least onecommon electrode 204 is parallel to the data lines 205. In addition, atleast one pixel electrode 230 is provided in the pixel region. The atleast one pixel electrode 230 is parallel to the at least one commonelectrode 204. The common electrode 204 can be made of the same materialas the gate line 202 a and can be formed on the same layer as the gateline 202 a. However, in order to improve an aperture ratio, the commonelectrode 204 may be formed of indium tin oxide (ITO) on the same layeras the pixel electrode 230. Liquid crystals are driven by an horizontalelectric field formed between the at least one common electrode 204 andthe at least pixel electrode 230.

In an embodiment of the present invention, an insulating layer (notshown) may be provided between the pixel electrode 230 and the commonelectrode 204. In addition, a part of the pixel electrode 230 overlapsthe gate line 202 a with an insulating layer interposed between, therebyforming a capacitor.

Although not shown in FIG. 2, a color filter layer is formed within eachpixel region. The color filter layer formed in each pixel regionincludes one of red, green and blue sub-color filter layers. The colorfilter layer is formed only within the pixel region. That is, the colorfilter layer is not formed on the gate line or the data line. Instead,black matrix parts 220 are formed on the gate lines 202 a and the dataline 205 for blocking undesired light emitted from a lower portionoutside the pixel region.

In embodiments of the present invention, the black matrix parts 220 areformed concurrently with the at least one pixel electrode 230 and areformed of an opaque metal thin film to prevent light leakage. The blackmatrix parts 220 are not formed on the same layer as the color filterlayer, but on the same layer as the at least one pixel electrode 230. Anopaque and thin metal layer can be used for the black matrix parts 220in order to block undesired light. For example, a Cr layer may be usedas the thin metal layer. However, since the Cr layer is highlyreflective to external light, a contrast ratio of the liquid crystaldisplay device may be reduced. Accordingly, a CrOx layer having a lowreflectance is formed on the Cr layer within the black matrix 220,thereby preventing the black matrix 220 from reflecting external light.

The black matrix 220 further includes a transparent electrode, such asITO (Indium Tin Oxide), forming a pixel electrode concurrently made withthe black matrix. Specifically, the Cr layer, the CrOx layer, and thetransparent electrode layer are laminated in a sequential order, and thethree layers are patterned concurrently to form the pixel electrode 230and the black matrix 220. However, the lamination sequence of the Crlayer, CrOx layer and the ITO layer may in general be one of: (a) Crlayer-CrOx layer-ITO layer; (b) Cr layer-ITO layer-CrOx layer; (c) ITOlayer-Cr layer-CrOx layer; (d) ITO layer-CrOx layer-Cr layer; (e) CrOxlayer-Cr layer-ITO layer; and (f) CrOx layer-ITO layer-Cr layer. Sincethe CrOx layer prevents reflection of the Cr layer, a laminationsequence in which the CrOx layer is formed under the Cr layer, cannot beused. Thus, in embodiments of the present invention, laminationsequences (d) ITO layer-CrOx layer-Cr layer, (e) CrOx layer-Cr layer-ITOlayer, and (f) CrOx layer-ITO layer-Cr layer are not used.

Since the CrOx layer has a weak electric conductivity, the laminationsequence (a), which is Cr layer-CrOx layer-ITO layer, cannot be used toform a gate pad or a data pad, where the lamination is made from the Crlayer. Also, the lamination sequence (c), which is ITO layer-Crlayer-CrOx layer, may cause an etchant of the Cr layer to penetrate theporous ITO layer and etch the gate pad or the data pad formed under theITO layer. Thus, among the lamination sequences listed above, thelamination order (b), which is Cr layer-ITO layer-CrOx layer, is used inembodiments of the present invention. The black matrix 220 resultingfrom such a lamination sequence prevents light leakage. Moreover, theblack matrix 220 and the pixel electrode 230 are concurrently formed.Thus, in embodiments of the present invention, the number of processescan be reduced.

As shown in FIG. 2, a gate pad electrode 202P is formed at an end of thegate line 202 a and a data pad electrode 205P is formed at an end of thedata line 205 to thereby supply externally provided signals to the gatelines 205 a and the data lines 205. In an embodiment of the presentinvention, the more conductive ITO layer is the uppermost layer of thegate and data pad. However, in accordance with the lamination sequence(b), which is Cr layer-ITO layer-CrOx layer, the CrOx layer covers theITO layer. Thus, portion of the CrOx layer overlapping the gate pad anddata pad is removed as described below.

FIG. 3A is a cross-sectional view of an exemplary pixel region alongline I-I′ in the array substrate of the liquid crystal display device ofFIG. 2. Referring to FIG. 3A, a gate electrode 202 and a plurality ofcommon electrodes 204 are formed on a substrate 201. The gate electrode202 and the common electrodes 204 may be formed of a conductive metallayer, such as aluminum or a dual layer of aluminum and molybdenum. Agate insulating layer 203 is formed on the gate electrode 202 and thecommon electrodes 204. For example, the gate insulating layer 203 mayinclude a silicon oxide (SiO₂) layer. A thin film transistor is formedon a TFT region of the gate insulating layer 203. The thin filmtransistor includes an active layer 208 formed of a semiconductor layer,and source and drain electrodes 206 and 207 connecting with the activelayer 208, respectively. The source and drain electrodes 206 and 207connect with the active layer 208. An ohmic contact layer 209 isinterposed between the source and drain electrodes 206 and 207.

A data line 205 is formed at a predetermined location on the gateinsulating layer 203. In addition, a silicon oxide (SiO₂) layer or asilicon nitride (SiNx) layer may be formed as an interlayer 211 on thesource and drain electrodes 206 and 207 and the data line 205. A colorfilter layer 211 is formed on the interlayer 210 within each pixelregion. The color filter layer 211 is formed only within the pixelregion so as not to overlap the gate line 202 a (shown in FIG. 2) andthe data line 205. The color filter layer 211 includes one of red, greenand blue sub-color filter layers. A passivation layer 212 is formed onthe color filter layer 211 to protect the components underneath. Thepassivation layer 212 may be formed of a transparent organic layer.

Black matrix parts 220 and pixel electrodes 230 are concurrently formedon the passivation layer 212. The pixel electrodes 230 are parallel tothe common electrodes 204. In one embodiment of the present invention,each of the pixel electrodes 230 is located between adjacent commonelectrodes 204. Thus, the pixel electrodes 230 and the common electrodes204 alternate with each other. Thus, the pixel electrodes 230 and the atthe common electrodes 204 form a pair of pixel and common electrodes.The black matrix parts 220 form a matrix on the gate lines 202 a (shownin FIG. 2), the data lines 205 and the TFT region. The color filterlayer is formed in areas surrounded by the black matrix parts 220.

In embodiments of the present invention, an opaque metal layer 213, suchas a Cr layer 213 for the black matrix, a transparent layer 214, such asan ITO layer 214 for the pixel electrodes 230, and a low reflectancelayer 215, such as a CrOx layer 215 for preventing the Cr layer 213 fromreflecting external light, are laminated in a sequential order to formthe black matrix 220 and the pixel electrodes 230. An alignment layer240 a for initial alignment of liquid crystals may be further formed onthe black matrix 220 and the pixel electrode 230. The black matrix 220covers the gate pad electrode 202P and the data pad electrode 205Pformed at the ends of the gate lines 202 a and the data lines 205. Anupper substrate 250 facing the array substrate 201 is formed at one sideof the array substrate, which includes the thin film transistors. Aliquid crystal material is filled between the array substrate 201 andthe upper substrate 250.

FIG. 3B is a cross-sectional view of an exemplary gate pad and anexemplary data pad along lines II-II′ and III-III′, respectively, in thearray substrate of the liquid crystal display device of FIG. 2.Referring to FIG. 3B, a gate pad includes a gate pad electrode 202P,which may be at one end of one of the gate lines 202 a. Portions of theCr layer 213, the ITO layer 214 and the CrOx layer 215, which form thepixel electrode 230 and black matrix 220, overlap the gate pad electrode202P. A data pad includes a data pad electrode 205P formed on the gateinsulating layer 203. Portions of the Cr layer 213, the ITO layer 214and the CrOx layer 215, which form the pixel electrode 230 and blackmatrix 220, overlap the data pad electrode 205P.

Since the gate pad and the data pad should respectively supply anexternally provided scan signal and an externally provided data signalto the gate lines 202 a and the data lines 205, and are in contact witha TCP (Tape Carrier Package) for connecting the pads with a drivingcircuit, the more conductive ITO layer should be exposed as theuppermost layer. Thus, in embodiments of the present invention, the CrOxlayer 215 on the ITO layer 214 is removed.

FIG. 4A is a cross-sectional view of an exemplary pad unit outside apixel region of a liquid crystal display panel in accordance with anembodiment of the present invention. FIG. 4B is a plan view of exemplarypad units outside a liquid crystal display panel in accordance with anembodiment of the present invention. Referring to FIG. 4 a, an arraysubstrate 200 and an upper substrate 420 are attached to each other by asealant 410, and liquid crystals are filled between the array substrate200 and the upper substrate 420. Common electrodes 204, data lines 205,and a color filter layer 211 are formed in the array substrate 200. Gatepads and data pads are formed outside the sealant 410 of the arraysubstrate 200. For example, as shown in FIG. 4A a gate pad 430,including a gate pad electrode 202P, is formed outside the sealant 420.As shown in FIG. 4B, the gate pad 430 is located outside the liquidcrystal display panel 400.

A weakly conductive CrOx layer is formed on an upper portion of the gatepad electrode 202P and has to be removed to expose a more conductive ITOlayer. Specifically, after the array substrate 200 and the uppersubstrate 420 are attached, the CrOx layer on the gate pad unit 202P issubsequently removed by an ashing process. As a result of the ashingprocess, a black matrix and a pixel electrode are formed using ametallic material, especially a dual layer of a Cr film and a CrOx film,and an ITO layer laminated together with the dual layer.

Accordingly, in accordance with embodiments of the present invention, aliquid crystal display device having a COT structure is provided. Eachof a gate pad and a data pad of the liquid crystal display deviceincludes laminated layers, including a Cr layer and an ITO layer. TheITO layer is exposed. A method of fabricating a liquid crystal displaydevice having a COT structure in which a pixel electrode and a blackmatrix are concurrently formed will be described with reference to FIGS.5A to 5F.

FIG. 5A is a cross-sectional view of the formation of exemplary gateelectrodes and common electrodes in a process of fabricating an arraysubstrate of a liquid crystal device in accordance with an embodiment ofthe present invention. Referring to FIG. 5A, gate electrodes 202 andcommon electrodes 204 are formed on the substrate 201, for example by aphotolithography process. Concurrently, a gate pad electrode 202P isalso formed at the gate pad portion of the substrate. Subsequently, agate insulating layer 203 is formed on the gate electrode 202 and thecommon electrodes 204, for example by plasma enhanced chemical vapordeposition (PECVD). The gate insulating layer 203 may be formed of ansilicon oxide layer.

FIG. 5B is a cross-sectional view of the formation of exemplary thinfilm transistors and data electrodes in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention. Next, referring to FIG. 5B, a thinfilm transistor is formed on the gate insulating layer and over the gateelectrode 202. The process of forming the thin film transistor includesforming an active layer 208 formed of a semiconductor layer on the gateinsulating layer 203 and over the gate electrode 202, and forming sourceand drain electrodes 206 and 207 contacting the active layer 208.

Concurrently with the source and drain electrodes 206 and 207, data padelectrode 205P and data lines 205 are further formed on the gateinsulating layer 203. The source and drain electrodes 206 and 207, thedata lines 205 and the data pad electrode 205P may be formed by aphotolithography process.

FIG. 5C is a cross-sectional view of the formation of exemplary layersof an interlayer and a color filter in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention. Referring to FIG. 5C, an interlayer210 subsequently is formed on the source and drain electrodes 206 and207. An inorganic insulating layer or an organic insulating layer may beused as the interlayer 210. After the interlayer 210 is formed, aphotosensitive color filter layer 211, including red, green, and bluesub-color filter layers, is formed on the interlayer 210. Specifically,a color filter layer 211, including one of red, green, and bluesub-color filter layers, is formed in each pixel region. The colorfilter layer 211 is not formed on upper portions of the gate line (notshown) and the data lines 205. After applying the photosensitive colorfilter layer 210 to the interlayer 210, the red, green and bluesub-color filter layers are formed at the respective pixel regions byphoto-mask processes. A passivation layer 212 is further formed on thecolor filter layer 211.

FIG. 5D is a cross-sectional view of the lamination of exemplary layersof metal, ITO layer and CrOx in the process of fabricating an arraysubstrate of a liquid crystal device in accordance with an embodiment ofthe present invention. Referring to FIG. 5D, following the formation ofthe passivation layer on the color filter layer 211, contact holes areformed to expose the gate electrode in the gate pad region, and the dataelectrode in the data pad region. Then, an opaque metal layer 213, anITO layer 214 used as a pixel electrode, and a CrOx layer 215 are formedon the passivation layer 212 in a sequential order. The opaque metallayer 213 may be a Cr layer. A triple layer of the opaque metal layer213, the ITO layer 214 and the CrOx layer 215 is concurrently formed onthe gate pad and the data pad.

Referring to FIGS. 5C and 5D, in another embodiment of the presentinvention, following the formation of the color filter layer 211 on theinterlayer 210, contact holes (not shown in FIGS. 5C and 5D) are formedto expose the gate electrode in the gate pad region, and the dataelectrode in the data pad region. The contact holes may concurrently beformed while forming a contact hole for exposing a drain electrode.Then, the passivation layer 212 is formed on the color filter layer 211after forming the contact holes on the gate pad and the data pad. Then,an opaque metal layer 213, an ITO layer 214 used as a pixel electrode,and a CrOx layer 215 are formed on the passivation layer 212 in asequential order. The opaque metal layer 213 may be a Cr layer. A triplelayer of the opaque metal layer 213, the ITO layer 214 and the CrOxlayer 215 is concurrently formed on the gate pad and the data pad.

FIG. 5E is a cross-sectional view of the formation of exemplary patternsof black matrix parts and electrodes in the process of fabricating anarray substrate of a liquid crystal device in accordance with anembodiment of the present invention. As shown in FIG. 5E, the opaquemetal layer 213, the ITO layer 214 and the CrOx layer 215 laminated inthe sequential order are patterned using a photolithography process. TheCrOx layer 215 and the ITO layer 214 may be etched using the sameetchant during the photolithography process. But, the opaque metal layer213 is etched using different etchant than for the ITO layer 214.However, if the opaque metal layer 213 may be etched by the same etchantbeing used for the ITO layer, only one etchant may be used for etchingthe triple layer. The black matrix parts 220, which cover regions wherethe gate line, the data line and the thin film transistor are to beformed, and the pixel electrodes 230, which supply an horizontalelectric field to liquid crystals, are formed by photolithography.Concurrently with the black matrix parts 220 and the pixel electrodes230, a gate pad pattern 202P′ and a data pad pattern 205P′, each ofwhich including laminated layers of the opaque metal layer 213, the ITOlayer 214, and the CrOx layer 215, are further formed on the gate padand the data pad.

As a result of these processes, an array substrate having a COTstructure using in-plane switching mode is formed, including the colorfilter layer, the pixel electrodes and the common electrodes formed onthe array substrate. Then, the array substrate and an upper substrate,which is formed by a separate process, are attached to each other. Whileattaching the upper and array substrates, a seal line (not shown) isformed on the array substrate. After the array substrate and the uppersubstrate are attached to each other by a sealant, the gate pad and thedata pad, which are formed outside the sealant are completed.Specifically, within the gate pad region and the data pad region, theconductive ITO layer should be exposed to provide electric contacts.

FIG. 5F is a cross-sectional view of the completion of exemplary gatepads and data pads in the process of fabricating an array substrate of aliquid crystal device in accordance with an embodiment of the presentinvention. Referring to FIG. 5F, after the array substrate and the uppersubstrate are attached to each other, since the gate pad unit and thedata pad unit are covered with the weakly conducting CrOx layer 215, theCrOx layer 215 is removed from the gate pad and the data pad regions. Anashing process is performed for removing the CrOx layer 215.Subsequently, a liquid crystal material (not shown in FIG. 5F) is filledin a space between the array substrate and the upper substrate by aliquid crystal injection process to complete the liquid crystal displaydevice.

In embodiments of the present invention, when fabricating a liquidcrystal display device having a COT structure using an in-planeswitching mode, the number of fabrication processes is reduced byconcurrently forming a black matrix and a pixel electrode. Inparticular, the black matrix and the pixel electrode layer arefabricated by using a plurality of laminated layers, in which the opaquemetal layer, the ITO layer and the CrOx layer are laminated in asequential order. Thus, the black matrix and the pixel electrode mayconcurrently be formed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice having structure of color filter on TFT and using in-planeswitching mode of the present invention without departing from thespirit or scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

1. A liquid crystal display device, comprising: gate lines crossing datalines on a first substrate defining a pixel region; at least one commonelectrode formed in the pixel region; at least one pixel electrode inthe pixel region, the at least one pixel electrode corresponding to thecommon electrode; a color filter layer formed within the pixel regionexcluding the gate line and the data line; a black matrix having atleast three layers, an inner layer of the at least three layers being anelectrode material.
 2. The device of claim 1, wherein the pixelelectrode and the black matrix have the same laminated layers.
 3. Thedevice of claim 1, wherein the at least three layers of the black matrixinclude a first layer of conductive opaque layer, a second layer ofelectrode material, and a third layer of reflective shielding layer in asequential order.
 4. The device of claim 3, wherein the first layer is aCr layer, the second layer is an ITO layer and the third layer is a CrOxlayer.
 5. The device of claim 1, wherein the at least one commonelectrode is formed in the same layer as the gate lines.
 6. The deviceof claim 1, further comprising a passivation layer formed on the colorfilter layer, wherein the black matrix and the at least one pixelelectrode are formed on the passivation layer.
 7. A method offabricating a liquid crystal display device, comprising: forming gatelines and a gate pad electrode on a first substrate; forming data linesand a data pad electrode on the first substrate; forming an interlayeron the data lines and the data pad electrode; forming a color filterlayer on the interlayer; forming a passivation layer on the color filterlayer; forming contact holes exposing the gate pad electrode and thedata pad electrode; and forming at least three layers on the colorfilter layer to form a black matrix and a pixel electrode, one of the atleast three layers including an electrode material.
 8. The method ofclaim 7, wherein forming at the least three layers includes forming afirst Cr layer, a second ITO layer, and a third CrOx layer on the colorfilter layer in a sequential order.
 9. The method of claim 7, whereinforming the color filter layer on the interlayer includes forming one ofred, green and blue sub-color filter layers in a pixel region defined bycrossing gate lines and data lines.
 10. The method of claim 8, whereinforming the at least three layers includes: forming at least threelayers on the color filter layer; forming a photoresist pattern on theat least three layers on the color filter layer; and forming the blackmatrix and the pixel electrode by patterning the at least three layersusing the photoresist pattern.
 11. The method of claim 8, furthercomprising; exposing the electrode material on the gate pad electrodeand the data pad electrode.
 12. The method of claim 11, wherein exposingthe electrode material on the gate pad electrode and data pad electrodeis performed after the first substrate is attached to an upper substratefacing the first substrate.
 13. The method of claim 11, wherein thethird layer is removed from the gate pad electrode and the data padelectrode by an ashing process.
 14. A liquid crystal display device,comprising: gate lines crossing data lines on a first substrate defininga pixel region; at least one common electrode formed in the pixelregion; at least one pixel electrode in the pixel region, the at leastone pixel electrode having at least three layers, and the at least onepixel electrode corresponding to the common electrode; a color filterlayer formed within the pixel region excluding the gate line and thedata line; a black matrix having a same at least three layers as the atleast one pixel electrode, an inner layer of the at least three layersbeing an electrode material.
 15. The device of claim 14, wherein the atleast three layers of the at least one pixel electrode include a firstlayer of conductive opaque layer, a second layer of electrode material,and a third layer of reflective shielding layer in a sequential order.16. The device of claim 15, wherein the first layer is a Cr layer, thesecond layer is an ITO layer and the third layer is a CrOx layer. 17.The device of claim 14, wherein the at least one common electrode isformed in the same layer as the gate lines.
 18. The device of claim 14,further comprising a passivation layer formed on the color filter layer,wherein the black matrix and the at least one pixel electrode are formedon the passivation layer.